Mucus secretion is a normal function of respiratory mucous membranes. Models for measurement of mucus production by cultured human and feline bronchial and nasal mucosa have been developed in order to examine the controls of mucus secretion. Using feline airway, PAF and GRP caused mucus secretions, and the isolated eosinophil granule protein, ECP, was even more active. Thus, we are continuing to analyze factors possibly participating in asthma for their actions on mucus secretion. We also compared our human in vivo challenge system with in vitro responses and confirmed that both models are necessary to explain nasal secretor controls. Alpha adrenergic agonists cause mucus secretion. Endothelin 1 was localized to glandular and vascular tissues in the nasal mucosa, was found in secretions and, in turn, caused the secretion of mucus in vitro. Moreover, ET-1 caused the nasal mucosa to generate eicosanoids, including HETE's. Inhibitors of the lipoxygenase pathway reduced ET-1 induced mucus secretion, suggesting that ET-1 in part, acts by causing lipoxygenase production.